Using an improved intracerebral microinjection technique developed in my laboratory, I have identified one area of the CNS (the periventricular-periaqueductal gray) which mediates morphine analgesia. However, there are probably other sites which are also involved in this action of morphine. I propose to continue my mapping studies of the CNS in order to identify these other sites. Since analgesic opiates have high dependence liability, it is reasonable to assume that such analgesic sites may also mediate opiate dependence. After identification of CNS sites which mediate morphine analgesia, I will investigate these sites for morphine dependence, using naloxone microinjections into these sites in morphine-dependent animals. Are these sites also involved in behavior which maintains opiate self-administration? After stable rates of lever-pressing for intrajugular morphine infusions are established, such rats will be microinjected with naloxone and changes in rate of responding will be observed.